Hydraulic power transmitting device



July 3, 1951 A. E. w. JOHNSON 2,558,960

HYDRAULIC POWER TRANSMITTING DEVICE Filed Jan. 28, .1950

INVENTOR ARNOLD EW. JOHNSON Patented July 3, 1951 HYDRAULIC POWER TRANSMITTING DEVICE Arnold E. W. Johnson, Oak Park, Ill., assignor to International Harvester Company, a corporation of New Jersey Application January 28, 1950, Serial No. 141,103

Claims. 1

This invention relates to an hydraulic power transmitting unit of a type serviceableas a power lift for a tractor and relatesmore particularly to such a. unit which selectively receives power from a continuously rotatingmember which may be a shaft or the like driven by a tractor engine.

The invention may be regarded as an improvement over the hydraulic power lift shown in 00- pending U. S. patent application", Serial No. 63,482, filed December 4, 1948, now Patent No. 2,524,055, issued October 3, 1950, in the name of Clarence A. Hubert and assigned to the assignee of the present application. The power lift disclosed in saidpatent includes a pump'continuously driven from the tractor engine. EX- cepting when the power lift of the patent is in operation. the fluid from the pump outlet is discharged at low pressure through asection of a pressure control valve; A- manually operated control valve, by virtue of opening a port of a control passage'fcr the pressure controlling valve, is operable to terminate the low pressure bypass condition concurrently with directing the fluid from the pump-to a hydraulic ramor motor of the power lift. The hydraulic ramand an operating lever for the control Valve are differentially connected with such valve whereby the ram is operable to returnthe valve to a closed position when the ram plunger has moved a distance and direction correlated with the distance and direction of movement of the operating lever. The control valve of said patent is of the plunger type movable axially within a bore therefor and because of this valve plunger controlling communication between the pump and ram as Well as controlling the control passage port, the valve plunger must be made with a high degree of precision. Manufacturing tolerances are required involving considerable care and correspondingly increase the production cost of the valve. When the various bores and passages of the ram, of the controlling valve and of the pres sure controlling unit are formed within a single casting, according to common practice, there is a further production problem of dislodging all of the metal chips made by the boring operations attendant to the formingof thesepassages.

A general object of this inventionv is the provision of an interruptabledrive between the pump and the continuously rotating driving member therefor and which is operated to establish the driving connection concurrently with movement of the control" valve from the closed position, this construction being employed as an expedient for providing fluid at high. pressure only during V sociated therewith and with control ports of the control valve are eliminated. It is thus possible to make the control valve plunger shorter and to have fewer port-controlling enlargements upon this plunger wherefor its production is less complicated and its cost decreased. Diminishing the number of bores, passages and ports attendant to the elimination of the pressure controlling device simplifies the network of passages and the removal of metal filings and chips therefrom.

Another object is the provision-of magneticfiuid clutch between the continuously rotating driving memberand the pump, this clutch having' a driving characteristic when subjectedto an overload permitting slippage between-its driving and driven parts while transmitting a constant maximum torque irrespective of therelative speed of such parts. This clutch is energized by an electric circuit under control of the member which is manipulated for controllingthe control valve plunger wherefor the clutch will establish its driving connection for the pump only while the control valve establishes communication between the pump and ram. The use of a clutch having the above described driving characteristic makes it possible to substantially instantaneously operate the pump without exerting excessive strain thereon or on the driving connections therefor. Structural details of the magnetic fluid clutch are disclosed in an article commencing. on page 639 of SA'E Quarterly Transactions for October 1949, vol. 3, No. 4.

Another object is the provision of a hydraulic accumulator in thefiuid line between the pump and the control valve together with an energizing circuit for the magnetic-fluid clutch and which circuit includes a switch operable responsively'to a predetermined minimum accumulatorpressur'e to energize the clutch for driving the'pump and to de-energ'ize the circuit and pump upon the accumulator pressure attaining a predetermined maximum.

The above and other desirable objects inherent in and encompassed by the invention will be more fullyunderstood from the ensuing description, the appended'claims and the annexed drawing.

The single figure of drawing is a partially diagrammatic illustration ofan hydraulic power 3 transmission unit embodying the preferred form of the invention.

With continued reference to the drawing, an hydraulic ram or motor l2 has a cylinder i3 and a piston M. A piston rod [5 is pivotally connected between the piston and the upper end form of a gear adapted to be driven from the engine of a tractor upon which the power-transmitting unit is mountable. .Fluid is returned to the pump through an inlet 24 and aconduit 25 leading from a sump-type reservoir 26 of the power-transmitting unit. 7

Assuming the pump 2| to be driven, fluid under pressure flows from the outlet l9 through a conduit 21, through an accumulator 28 and an admittance port 29 into a cylindrical bore 3| of a control valve 32. This valve bore 3| has two ports 33 and 34 adapted to be simultaneously closed by enlargements or lands 35 and 36 upon a valve plunger 31 which is axially movable within the bore. A reversible flow passage 38 is communicative between the valve port 34 and a port 39 at the piston rod end of the ram cylinder l3. A second reversible flow passage 4| is communicative between the valve port 33 and a port 42 at the opposite end of the ram cylinder. Passage 38 contains a check valve 43 in series therewith. This check valve includes a valve member 44 urged upon an annular seat 45 by a spring 46. The valve member 44 is adapted to be 'held unseated, as illustrated, by pressure of fluid in the passage 4| upon a piston 41 which exerts a thrust through a stem 48 against the valve member 44. Resersible flow passage 4| contains a check valve 49 including a valve member 5| urged upon an annular seat 52 by a spring 53. This check valve is openable by fluid flowing from the port 33 through the passage 4|, as illustrated in the drawing. This valve is also openable by the pressure of fluid in the reversible flow passage 38 against a piston 54 which is thereby operable to exert a thrust'force through the stem 55 against the valve member 5| for opening the valve 49 during a phase in the operation of the device which will be later explained. During such later explained phase in the operation of the unit the fluid will be flowing from the valve port 34 and through the reversible flow passage 38 and will be operable to unseat the valve member 44 to some position as that shown in the drawing while concurrently forcing the piston 41 against a shoulder 56. This is similar to the action of the fluid under pressure in the reversible flow passage 4| in holding the piston 54 against a shoulder 51. V

The control valve plunger 31 is differentially controlled by a manual control lever 5| and the ram l2. The lever BI is pivotal about a fixed pivot 82 and has its lower end connected with the lower end of a walking beam lever 63 by a link 64. The ram piston is operably connected with the upper end of the walking beam lever glgrough the connecting rod l5, arm l6, and a link A cam head 66 on the right-hand of the plunger 31 cooperateswith a cam follower 51 on an endwise reciprocal stem 68 of a switch 69.

This switch is open when the cam 66 registers with a notch 1| in the cam follower head thereby permittin the stem 38 to project a short distance endwise downwardly. While the cam 66 registers with either of the lobes 12 or 13 on the follower 61, the switch will be closed. The switch 69 constitutes part of an electrical circuit commenoing with ground G and leading through a conductor 14, switch 59, a conductor 15, magnetic-fluid clutch 22, a conductor 16, and the tractor storage battery 11 to ground at G.

An auxiliary electrical circuit for controlling energization of the magnetic-fluid clutch 22 includes a fluid pressure responsive switch 18 communicative with the accumulator 28 through the conduit 21 and a conduit 79. The auxiliary circuit startswith the ground at G" and leads through the switch 18, a conductor 8|, a portion both ports 33 and 34.

Operation of the apparatus While all parts of the apparatus are at rest,

7 with the exception of the continuously rotating driving member 23, the control valve plunger 31 will be in the closed or neutral position N, that V is with the index mark M of the plunger in alignment with the scale mark N. At that time the plunger enlargement 35 will register with the port 33 and enlargement 36 will register with the port 34, closing these two ports. The cam 66 on the right end of the plunger will be centered in the cam follower recess 1| causing the switch 69 to be open. Assuming the fluid pressure in the accumulator 28 to be above the minimum pressure to be maintained therein, the pressure responsive switch 18 will also be open and the magnetic-fluid clutch 22 de-energized.

The drawing illustrates the apparatus in the status it assumes immediately following movement of the control lever 6| clockwise about the pivot 62 for incurring clockwise movement of the rock shaft l7. When the operator pivoted the control lever Bl clockwise, this lever was operable through the link 54 to swing the lower end of the walking beam lever 53 to the left for moving the plunger 31 endwise into the open position A. Concurrently with this endwise movement of the valve plunger, the cam 35 passed under the cam follower profile 12 for closing the switch 69 and consequently engaging themagnetic-fluid clutch. Thereupon the continuously rotating member 23 is drivingly connected with the pump 2| whereby fluid is discharged through the pump outlet l9, conduit 21, accumulator 29, valve port 29, valve port 33, reversible flow passage 4| andthe check valve 49 therein into the left end of the ram cylinder l3. The pressure of fluid in the reversible flow passage 4| is exerted against the left end of the valve operating piston 41 which moves to the right for unseating the valve member 44 wherefor the ram piston i 4 can move to the right under the influence of the pressure fluid in the left end of the cylinder |3 incident to exhausting the fluid from the piston rod end of the cylinder through the reversible flow passage 38, past the check valve 43 therein and into the reservoir 26 through port 34. Fluid flows from the reservoir 26 through the conduit 25 and thus through the pump inlet 24'. As soon as the rock shaft H has rocked clockwise a distance correlated with the pivotal movement of the manually-operated lever 6|, the walking beam lever 63 will have been pivoted sufficiently far clockwise about its pivotal connection with the link 64 for returning the valve plunger to the neutralposition'N; Thereupon the switch 69 is openedandthe valve ports 33 and 34closed. The springs 46and 53 close the check valves 43 and Hand thereby hydraulically lock the ram piston I4- against movement in either direction.

When it is desired to rock the rock shaft counter-clockwise the lever 6| will be manually movedcounter-clockwise to swing the lower end of the walking beam lever 63 to the right for carrying the valve plunger 3'! to position B wherein communication is established between the ports 29 and 34, and to establish communication between the port 33 and the reservoir 26. The cam 66 will have been moved into registry with the cam lobe T3 for closing the switch 69 whereupon the clutch 22 operabl connects the pump with the continuously rotating driving member 23. Fluid under pressure will then flow from the accumulator through the ports 29 and 34, through the reversible flow passage 38 and the check valve 43 therein into the piston rod end of the ram cylinder 3. The fluid in the reversible flow passage 38 will press against the right end of the valve operating piston 54 for shifting the stem 55 against the valve member 5| to hold the latter unseated from the seat 52. Consequently the plunger M can move to the left under the influence of the fluid under pressure in the right end of the cylinder I3 incident to exhausting fluid through the reversible flow passage 4| and the opened check valve 49, and thence through the port 33 into the reservoir 26. When the ram plunger M has moved to the left a distance correlated with the distance of movement of the hand lever 6| counter-clockwise the valve plunger will disconnect the switch 69 and close the valve ports 33 and 34 to re-establish the quiescent condition of the apparatus while it is disconnected from the continuously driving member 23.

Having thus described a single preferred form of the invention with the view of clearly and concisely illustrating same, I claim.

1. In an hydraulic power transmitting unit receivable of driving force from a continuously rotating driving member; a hydraulic motor operable responsively to admittance of fluid under pressure into an inlet thereof; a pump having a fluid outlet; fluid conducting means including a control valve interposed between said motor inlet and the pump outlet, the control valve being adjustable from a closed condition wherein it is effective for blocking communication through the fluid conducting means from the pump outlet to the motor inlet to an open condition establishing such communication through the fluid conducting means; a control member manipulatable for adjusting the valve from the closed condition to the open condition; means operable by the motor pursuant to operation thereof for resetting the valve to the closed condition; an electro-magnetic clutch interposed between said continuously rotating member and the pump and energizable for transmitting driving force from such rotating member to the pump, said electro-magnetic clutch having a driving characteristic when subjected to an overload of permitting slippage between its driving and driven parts while transmitting a constant maximum torque irrespective of the relative speed of such parts; and an electric energizing circuit operable in timed relation with'said'valve to energize the clutch pursuant to opening of the control valve and to de-energize the clutch pursuantto closing of the valve.

2. The combination set forth in claim 1 wherein said control valve includes port means in series with the fluid conducting means and a valve member occupying a position covering'the port means when the valve is closed and movable into a position uncovering the port means whenthe valve is open; and wherein the electric energizing circuit includes a switch controlling the energization status of said circuit and operated by said valve member.

3. The combination set forth in claim 1 wherein said fluid conductingmeans includes a hydraulic accumulator having a chamber through which fluid flows en route from the pump outlet to the motor inlet; and wherein there is a second electric energizing circuit for the electro-magnetic clutch and including a pressure-responsive switch unit subjected to the fluid pressure in said accumulator and operable attendant to a predetermined diminution of the pressure in the accumulator to energize such second circuit and the electro-magnetic clutch and operable attendant to the attainment of a predetermined maximum pressure of the fluid in the accumulator to de-energize such second circuit and the electromagnetic clutch.

4. The combination set forth in claim 3 wherein said control valve includes port means in series with the fluid conducting means and a valve member occupying a position covering the port means when the valve is closed and movable into a position uncovering the port means when the valve is open; and wherein the electric energizing circuit includes a switch controlling the energization status of said circuit and operated by said valve member.

5. In an hydraulic power transmitting unit receivable of driving force from a continuously rotating driving member; an hydraulic motor alternatively drivable in opposite directions; passages communicative with said motor for causing operation thereof in respective of such opposite directions when fluid is delivered to such motor respectively therethrough, each of said passages also being for the exhaust of fluid from the motor attendant to deliver through the other passage; check valves in said passages and operable when closed to preclude exhaust of fluid therethrough; fluid-operated devices respectively associated with said check valves and operable when subjected to a status of pressure differential to open their associated check valve to accommodate exhaust of fluid from the motor; a pump having a fluid outlet; a control valve having a cylindrical bore with axially-spaced ports from which said passages respectively lead, a fluid admittance port s 7 ered by its associated land to communicate with the reservoir, each of said fluid-operated devices being communicative with the passage of the nonassociated check valve for being subjected to the pressure of fluid admitted through such passage and operable thereby to open the associated check valve; a pump having an inlet communicative with said reservoir and an outlet communicative with said admittance port; means operable by said motor pursuant to operation thereof for resetting the valve plunger to the valve-closing position; an electro-magnetic clutch interposed between said continuously rotating member and the pump and energizable for transmitting driving force from such rotating member to the pump, said electro-magnetic clutch having a driving characteristic when subjected to an overload of permitting slippage between its driving and driven parts while transmitting a constant maximum torque irrespective of the relative speed of such parts; and an electric energizing circuit operable in timed relation with said valve plunger to energize the clutch pursuant to movement of the plunger in either axial direction from the closed position and for de-energizing the clutch pursuant to return of the valve plunger to the valve closing position.

ARNOLD E. W. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Piron Sept. 28, 1943 

